The present invention relates to electrical machines such as (but not limited to) electrical generators and, more particularly, to a generator rotor having a rotor which corrects for stiffness dissymmetry.
In a conventional generator having a rotor and a stator, the rotor is typically provided with field windings that excite the generator while receiving a current from a current source. The stator is provided with armature windings from which electrical power is output. Typical rotor construction requires that a field winding be assembled, bar by bar, in the radial cross-slots milled into the generator rotor. Containment of the rotor field windings within the slots milled in the rotor body is typically achieved using rotor wedges, rotor teeth and retaining rings.
The slots milled in the generator rotor induce stepwise changes in stiffness along the length of the rotor body. These changes in stiffness can be a source of fretting of parts that span these slots. The behavior of the rotor in response to power system disturbances has typically been addressed by providing a damper circuit through the dovetails of the rotor wedges that prevent the rotor field windings from lifting out of the rotor slots under a centrifugal load. A circuit between adjacent rotor slots has been completed by providing a shorting strap that lies under the retaining rings at each end of the rotor body.
The dynamic performance and system behavior of a turbine-driven generator drive train is very dependent upon the stiffness, mass and specific architecture of its constituent parts. It would therefore be desirable to tune properties and capabilities of the constituent parts to optimize the performance of the generator drive train. For example, it would be desirable to be able to tune the properties and capabilities of the generator drive train by adjusting the stiffness of the rotor body to correct any dissymmetry in stiffness of the rotor body. It would also be desirable to provide air gap adjustment between the rotor and stator of the electrical generator.